Universality classes in nonequilibrium lattice systems

This work is designed to overview our present knowledge about universality classes occurring in nonequilibrium systems defined on regular lattices. In the first section I summarize the most important critical exponents, relations and the field theoretical formalism used in the text. In the second section I briefly address the question of scaling behavior at first order phase transitions. In section three I review dynamical extensions of basic static classes, show the effect of mixing dynamics and the percolation behavior. The main body of this work is given in section four where genuine, dynamical universality classes specific to nonequilibrium systems are introduced. In section five I continue overviewing such nonequilibrium classes but in coupled, multi-component systems. Most of the known nonequilibrium transition classes are explored in low dimensions between active and absorbing states of reaction-diffusion type of systems. However by mapping they can be related to universal behavior of interface growth models, which I overview in section six. Finally in section seven I summarize families of absorbing state system classes, mean-field classes and give an outlook for further directions of research.Comment: Updated comprehensive review, 62 pages (two column), 29 figs included. Scheduled for publication in Reviews of Modern Physics in April 200

Robust exponential decay of correlations for singular-flows

We construct open sets of Ck (k bigger or equal to 2) vector fields with singularities that have robust exponential decay of correlations with respect to the unique physical measure. In particular we prove that the geometric Lorenz attractor has exponential decay of correlations with respect to the unique physical measure.Comment: Final version accepted for publication with added corrections (not in official published version) after O. Butterley pointed out to the authors that the last estimate in the argument in Subsection 4.2.3 of the previous version is not enough to guarantee the uniform non-integrability condition claimed. We have modified the argument and present it here in the same Subsection. 3 figures, 34 page

Global stabilization of feedforward systems under perturbations in sampling schedule

For nonlinear systems that are known to be globally asymptotically stabilizable, control over networks introduces a major challenge because of the asynchrony in the transmission schedule. Maintaining global asymptotic stabilization in sampled-data implementations with zero-order hold and with perturbations in the sampling schedule is not achievable in general but we show in this paper that it is achievable for the class of feedforward systems. We develop sampled-data feedback stabilizers which are not approximations of continuous-time designs but are discontinuous feedback laws that are specifically developed for maintaining global asymptotic stabilizability under any sequence of sampling periods that is uniformly bounded by a certain "maximum allowable sampling period".Comment: 27 pages, 5 figures, submitted for possible publication to SIAM Journal Control and Optimization. Second version with added remark

Dosimetric Characteristics of Gamma-Neutron Detectors DTGN-2

Abstract DTGN-2 (7LiF:Mg,Ti) gamma-neutron detectors are prepared as monocrystal discs 10 mm across and 3 mm thick. Selective determination of gamma and neutron doses in mixed gamma-neutron fields with these detectors is based on the use of two peaks on the glow curve whose efficiencies have different dependence on the LET. The method based on this effect has been developed to separate the gamma and neutron doses. Dose dependence obtained after neutron irradiation is linear in the range of 10-3 - 50 Gy and the minimum measurable dose is 5x10-4 Gy. Neutron sensitivities, expressed as gamma Gy per Gy, are 0.6, 0.8 and 1.1 with mean energies 1.9, 4.5 and 14 MeV, respectively. The parameters obtained permit possible application of the detector in accident dosimetry.</jats:p

Design of thermoelectric cooling devices

The advantages and applications of thermoelectric cooling in marine systems are considered. The program for calculating thermoelectric modules and designing the basic units of the cooling system is described.</jats:p